Process for the production of color photographic images



Sept. 29, 1953 P. D. DREYr-uss PROCESS FOR THE PRODUCTION OF COLORPHOTOGRAPHIC IMAGES Filed April l5, 1949 y INVENTOR QA-WL @1v/w12@ffy/fuss,

Patented Sept. 29, 1953 PROCESS FOR THE PRODUCTION OF COLOR PHOTOGRAPHICIMAGES Paul Daniel Dreyfuss, Van Nuys, Calif., assignor, by mesneassignments, to Bela Gaspar, Beverly Hills, Calif.

Application April 15, 1949, Serial No. 87,851

6 Claims.

This invention relates to the production of dye images from photographicsilver images by a process which comprises the synthesis of an azo dyein the exposed photographic emulsion layer.

In the United States Letters Patent 2,071,688 dated February 23, 1937 isdescribed and claimed a method of producing color photographic images inwhich the photographic layer is subjected to two treatments, the firsttreatment consisting of the conversion of a dye-forming substance into adye, and the second treatment consisting of the local dye destruction atthe required points. Thus, for example, a diazo compound is transformedinto an azo dye by coupling with a phenol; or a phenol or other azocoupler is transformed into an azo dye by treatment with a diazocompound, the azo dyes thus formed then being destroyed locally. In thesame patent is described and claimed an alternative process in which therst treatment consists of the local destruction of the dye-formingsubstance; the second treatment then consists of the conversion of theremaining dye-forming substance into the dye. Further alternativeprocesses are described in the U. S. Patents 2,166,049; 2,271,176;2,333,126; 2,361,541; 2,368,463 and in the co-pending patentapplications S. N. 518,256 iiled January 14, 1944, now Patent No.2,514,233, and S. N. 541,282 led June 20, 1944, now abandoned.

It is known that diazo compounds are easily reduced by metallic silver,particularly in the presence of acids. This behaviour of diazo compoundscan successfully serve to produce dye images directly from couplingcomponents in one step. This process has the advantage of simplicity,but it is sometimes diflicult to control. A much better control isobtained when the diazo compound is decomposed at a pH which is lowenough to avoid coupling at this stage, the coupling being performed ina successive step at a higher pH as described in Letters Patent2,271,176.

The process, described hereafter, in spite of requiring some additionalprocessing steps has the advantage of being controlled with particularease and of giving more reproducible results as regards density andgradation of the dye images.

The object of the present invention is the process which consists of arst treatment whereby a dye-forming substance is converted into adiffusely dispersed dye and in a second treatment whereby the dye isdestroyed locally at the required points. More particularly, it is theobject of this invention to provide a novel process whereby the contactof free diazo compounds with metallic silver is avoided, the metallicsilver images being converted, prior to the diazo treatment, into suchother images which are inert towards diazo compounds, said other imagesbeing capable of reacting directly or indirectly with the azo dyesformed in the coupling.

Whereas diazo compounds are decomposed by metallic silver in thepresence of acids, they are stable in the presence of silver salts. Itis therefore possible to produce a dye image in the following way: Aphotographic material comprising at least one silver halide emulsionlayer and an azo coupling component diffusely distributed therein isexposed to light, developed and nxed. Thereupon the metallic silverimage is converted into a rsilver salt image and the azo couplingcomponent is coupled with a diazo compound whereby a homogeneous dyeingis produced. The silver salt image is reconverted into a metallic silverimage, and the dye is destroyed locally where metallic silver ispresent. After removing the silver, a dye image is obtained.

The accompanying drawing shows a flow diagram of a modication of theprocess according to the invention.

The difference in the results between previously known procedures andthe process of the present invention is clearly shown by the comparativesteps described in Example l below.

Example 1 (a) A light sensitive silver halide emulsion layer is treatedin a bath containing 1% N-toluenesulfo-H-acid, thereupon in a solutioncontaining 1% diphenylguanidine acetate, washed and dried. The layer isexposed, developed and iixed in the usual manner. Instead ofimpregnating the layer with the diphenylguanidine salt oftoluenesulfo-H-acid before the exposure, the impregnation may also beeffected with the exposed and developed layer containing the silverimage.

(b) The layer, treated as above, is immersed in a strongly acid diazosolution, e. g., in a solution containing 0.5% diazotized sulfanilicacid and 1% hydrochloric acid. Thereupon the layer is immersed in asodium acetate or sodium carbonate solution. The silver is oxidized inan acid copper chloride bath and removed in ahypo bath. A reversedmagenta dye image is obtained.

(c) The layer, treated as described in Section a, is immersed in an acidcopper chloride bath 3 and washed. Thereupon it is treated in an aciddiazo solution and in a buffering solution as described in Section b,and finally the silver is removed in a hypo bath. A uniformly magentadyed layer is obtained which shows no trace of an image.

(d) The layer, treated as described in Section a, is immersed in an acidcopper chloride bath and washed. Thereupon it is treated in an aciddiazo solution and in a buffering solution as described in Section b.The silver salt image is reduced in a developer to metallic silver andthe azo dye is then destroyed locally in a bleaching bath containing 2%hydrochloric acid and 0.002 2,3-diaminophenazine. After the oxidation ofthe residual silver in an acid copperA chloride bath and after itsremoval in a hypo bath, a reversed magenta dye image is obtained. l y

A comparison of the images obtained in the processes b and d shows thatthe image (d) has much better definition than the image (b) The image(a) being a step wedge which shows 12 steps, the image (d) shows to 11steps, whereas the image (b) shows only 8 steps. Furthermore the image(d) has much clearer whites at the places of complete bleaching than hasthe image (b).

As the decomposition of diazo compounds by metallic silver is speeded upby strong acids, the inactivation of the silver image is of particularimportance whenever the photographic material must be treated with diazocompounds in the presence of strong acids. This is the case when diazocompounds, such as 1,4-phenylene-tetrazonium borofluoride or2-bromo-4-nitrobenzenediazonium sulfate, stable only in acid solution,are being used. Other compounds such as antidiazotates,nitrosoarylamides or diazoamino compounds sometimes need strong acidsfor their conversion into diazonium salts. Still other diazo compoundsare best coupled in acid solutions. In all these cases, a homogeneousdyeing of the photographic material is more readily obtained with aprocess which includes the previous inactivation of the silver image.

This inactivation of the silver image is effected after the development.The removal of the undeveloped silver halide is not necessary at thisstage, as it is possible to convert the metallic silver into a compoundwhich is different from the original silver halide; e. g., a layercomprising silver chloride and a silver image is treated in a copperbromide bath. Silver chloride and bromide are attacked with differentease by reducing agents and they have different solubilities in silversalt solvents. It is therefore possible to convert one of said saltsinto metallic silver while the other of said salts is removed after theazo coupling has taken place.

The preferred inactivated image consisting of silver chloride or silverbromide as the metallic silver image is easily converted into suchsilver salt image, and this silver salt image can easily be convertedinto a metallic image which is able to react with the azo dye, with noloss in image details through this chain of reactions.

However, this invention is not limited to the conversion into saidsalts. The metallic silver images may be converted into silverthiocyanate, into a mixture of silver chloride and mercurous chloride,into complex salts such as ferrocyanides and other compounds which arewell known in the arts of reduction, intensiiication and toning ofsilver images. Many of these compounds are inert with regard to diazocompounds and after- 4 wards can serve for the local destruction of theazo dyes.

The method, consisting of the inactivation of the metallic silver imageis suitable for obtaining diffusely dyed layers by diazo coupling, nomatter how the diazonium salt is brought into contact with thephotographic layers. For example, the diazo compound may be dissolved ina photographic bath which is acid or alkaline or it may be producedwithin the photographic layer from a diazo forming substance evenlydistributed therein.

Eample 2 The following layers are coated in successive order on atransparent film base:

1. A red sensitive silver halide emulsion, having incorporated thereinthe dye 4-nitraniline-2- sulfonic acid- N-benzoyl-1,5-aminonaphthol inits weakly colored (acidic) form.

2. A silver halide emulsion, which is sensitized for green light andwhich contains the coupling component N-N(naphthalene 1,5 disulfo) -8-amino-1naphthol3,6disulfonic acid and the diazo-forming component2,2-disulfodiphenyl- 4,4-bis-diazopiperidide, both componentsprecipitated with the base described in Example 2 of U. S. Patent2,317,134, namely, anhydrobiguanidobenzylalcohol acetate.

3. An interlayer containing colloidal silver.

4. A blue sensitive silver halide emulsion containing1,1-l2,2disulfodiphenylene(4.4)l-bis- [pyrazolone-()-carboxylicacid-(3)] and the same diazo-forming component and precipitating agentas in layer (2) above.

The diazo-forming component 2,2'disulfodi phenyl-4,4-bis-diazopiperidideis prepared by tetrazotiziiig benzidine-2,2'-disulfonic acid and pouringthe tetrazotized solution into an aqueous piperidine solution. Thebarium salt of tlie piperidide is isolated as an oil which is washedwith water. It becomes solid by washing with ethanol.

The multilayer material, produced in the indicated manner, is exposed tolight, developed and fixed. Thereupon, the superimposed silver imagesare iehalogenized in a potassium icrricyanide potassium bromide bath.The piperidide is split in a diluted hydrochloric acid bath and thetetrazonium salt, freed in this last bath, is coupled with the azocomponents by immersing the material in a sodium acetate bath. Thesilver salt image is reduced in an alkaline developer, and all three ofthe azo dyes are destroyed in the places where silver is present, e. g.,according to Reissue Patent 22,308. The residual silver is oxidized inan acid copper chloride bath and removed in a hypo bath. Finally the lmis treated in an alkaline bath to turn the dye in the bottom layer intoits cyan form, and dried.

The splitting of the piperidide and the coupling of the components toform the azo dye can be performed in a single step, i. e., thehydrochloric acid bath and the sodium acetate bath of the abovedirections are omitted and replaced by a diluted acetic acid or anacetic acid-sodium acetate bath. If the pH of this bath is high enoughto ease the coupling, the splitting takes place only slowly. If, on theother hand, the pH is low enough to allow the splitting in a short timethe coupling becomes sluggish. A method permittin T the splitting andcoupling in one step consists oi' the exposure of the weakly acidicbuiered material to a higher temperature, e. g., by hanging the buiieredmaterial in an air current of 50 C. Furthermore, it was found that thesplitlfrom the green sensitive emulsion layer (2) and from the bluesensitive emulsion layer (4) and incorporated instead in the interlayer(3).k

Example 3 A red sensitive emulsion containing the azo coupling component.naphthalene-1,5di-(sulfonaphthionyl-1,5aminonaphthol) is coated on atransparent base. On top of this emulsion layer is coated a cleargelatin interlayer and then a high speed green sensitive emulsioncontaining the n-amyl ether of m-(l\l,N-diethylamino) -phenoi. Thereuponfollows a gelatin layer containing a yellow filter dye, and finally thetop layer consisting of a blue sensitive emulsion containingN,Ndecamethylene-bis(2,4 dioxo 1,2,8,4 tetrahydroquinoline) The materialis exposed, developed, fixed, rehalogenized in an acid copper chloridebath and treated for 7 minutes in a bath containing 1% acetic acid and0.1% 4-nitro-l-diazonaphthalenec-sulfonic acid. Thereupon it isdeveloped again and treated in a dye destruction bath as in theforegoingexample. After the silver is removed in known manner thematerial is immersed for a short time in an aqueous solution containing0.4% ethanolamine and 3% polyethylene glyco1 300 (Carbide & CarbonCorp). After drying, a photograph in natural colors is obtained.

Further applications of this invention are obvious for anyone skilled inthe art. For exam- Die, a multilayer material comprising threesuperimposed silver images may be partially rehalogenized before thecoupling. The parts containing metallic silver will produce morecontrasty dye images than the parts containing the rehalogenized image.The material may be locally rehalogenized by controlled diffusion of arehalogenizing or of a redeveloping solution or by local application ofthe reagents; e. g., the dye formation in the sound track of a film isavoided by the presence of metallic silver only in the sound track,whereas the other parts of the lm are rehalogenized.

Having described my invention, what I claim as new, and desire toprotect by Letters Patent 1s:

T. claim:

1. In a process of producing a photographic dye image which includesexposing and developing a silver halide emulsion layer to produce ametallic silver image in said layer, the steps which comprise convertingthe metallic silver image in the developed emulsion layer into a silversalt image which is different from any remaining silver halide stillcontained in the layer and which is inert to diazo compounds in acidbaths, then treating the emulsion layer containing such silver saltimage with a diazo compound under an acid condition, coupling Withinsaid layer said diazo compound with an azo coupling component in thepresence of said silver salt image to dye said layer and developing ametallic silver image in said layer from a silver salt thereinanddestroying said azo' dye in said layer inproportion to the metallicsilver image in said layer.

2. In a process of producing a photographic dye image Which includesexposing and developing a silver halide emulsion layer to produce ametallic silver image in said layer, the steps which comprise convertingthe metallic silver image in the developed emulsion layer into a silverhalide image Which is different from any remaining silver halide stillcontained in the layer, then treating the emulsion layer containing suchsilver halide image with a diazo compound under an acid condition,coupling Within said layer said diazo compound with an azo couplingcomponent in the presence of said silver halide image to dye the layer,developing a metallic silver image in said layer from a silver halidetherein and destroying said azo dye in said layer in proportion to themetallic silver image within the layer to form a photographic dye image.

3. In a process of producing a photographic dye image the steps whichcomprise exposing a silver halide emulsion layer, developing said layerto produce a metallic silver image in the presence 0f an undevelopedimage of said silver halide, converting the metallic silver image insaid layer into an image of a silver halide other than the firstmentioned silver halide, then treating the emulsion layer containingsaid silver halide images with a diazo compound under an acid condition,coupling within said layer said diazo compound With an azo couplingcomponent in the presence of said silver halide images'to dye the layerdiffusely, developing a metallic silver image in said layer from one ofsaid silver halide images and destroying said azo dye in said layer inproportion to the metallic silver image Within the layer to form aphotographic dye image.

4. In a process of producing a photographic dye image the steps whichcomprise exposing a silver halide emulsion layer, developing said layerto produce a metallic silver image, fixing out any remaining undevelopedsilver halide, converting the metallic silver image in said layer intoa. silver halide image, then treating the emulsion layer containing saidsilver halide image with a diazo compound under acid conditions,coupling within said layer said diazo compound with an azo couplingcomponent in the presence of said silver halide image to dye said layerdiifusely, developing a metallic silver image from said silver halideimage and destroying said azo dye in said layer in proportion to themetallic silver image within the layer to form a photographic dye image.

5. In a process of producing a photographic dye image which includesexposing and developing a silver halide emulsion layer containing an azocoupling component to produce a metallic silver image in said layer, thesteps which comprise converting the metallic silver image in thedeveloped emulsion layer into a silver salt image which is diierent fromany remaining silver halide still contained in the layer and which isinert to diazo compounds in acid baths, then treating said layercontaining said silver salt image with a solution of a diazo compoundunder acid conditions, coupling the diazo compound with the azo couplingcomponent within the layer in the presence of said silver saltI image todye such layer diifusely, developing a metallic silver image in saidlayer from a silver salt therein and destroying said a-zo dye in saidlayerzin proportion to the metallic silver image in said layer.

6. In a process of producing a photographic dye image which includesexposing Vand developing a silver halide emulsion layer to yproduce Aametallic silver image in said layer, the .steps which compriseconverting the metallic silver image .in the developed emulsion layerinto .asilver salt image which is different from any remaining silverhalide still contained in the layer and which is inert to diazo-compounds in 'acid baths, then forming a, diazo compound withinsaid.layer containing said silver salt image under an acid condition,coupling within said layer vsaid diazocompound 'with .an azo couplingcomponent in the presence of said silver saltmage to :dye said layer anddeveloping a metallic silver image in `s'aicl layer yfrom a silver salttherein .and destroying .-8 said azo dye in said layer in proportion tothe metallic .silver image in said layer.

.PAUL DANIEL DREYFUSS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,758,572 Lierg May 13, 1930 2,132,154 .Gaspar Oct. 4, 19382,179,228 Eggert et al. Nov. 7, 1939 2,251,965 Verkinderen Aug. 12, 1941'2,333,126 Schwarc Nov. 2, 1943 2,350,736 Ehrenfried June 6, 19442,376,822 Schneider et al May 22,1945

FOREIGN PATENTS Number Country Date -503,873 Great Britain Apr. 17, 1939

1. IN A PROCESS OF PRODUCING A PHOTOGRAPHIC DYE IMAGE WHICH INCLUDESEXPOSING AND DEVELOPING A SILVER HALIDE EMULSION LAYER TO PRODUCE AMETALLIC SILVER IMAGE IN SAID LAYER, THE STEPS WHICH COMPRISE CONVERTINGTHE METALLIC SILVER IMAGE IN THE DEVELOPED EMULSION LAYER INTO A SILVERSALT IMAGE WHICH IS DIFFERENT FROM ANY REMAINING SILVER HALIDE STILLCONTAINED IN THE LAYER AND WHICH IS INERT TO DIAZO COMPOUNDS IN ACIDSBATHS, THEN TREATING THE EMULSION LAYER CONTAINING SUCH SILVER SALTIMAGE WITH A DIAZO COMPOUND UNDER AN ACID CONDITION, COUPLING WITHINSAID LAYER SAID DIAZO COMPOUND WITH AN AZO COUPLING COMPONENT IN THEPRESENCE OF SAID SILVER SALT IMAGE TO DYE SAID LAYER AND DEVELOPING AMETALLIC SILVER IMAGE IN SAID LAYER FROM A SILVER SALT THEREIN ANDDESTROYING SAID AZO DYE IN SAID LAYER IN PROPORTION TO THE METALLICSILVER IMAGE IN SAID LAYER.